1. Field of the Invention
Embodiments of the present invention generally relate to apparatus, systems, and processes for producing syngas. More particularly, embodiments of the present invention relate to apparatus, systems, and processes for reforming a hydrocarbon in a reforming furnace having pre-reformer tubes disposed in a transition section thereof.
2. Description of the Related Art
Hydrocarbon reforming furnaces are used to convert hydrocarbons such as naphtha and natural gas, among many possibilities, to syngas, which typically contains hydrogen and carbon monoxide. Syngas can also include varying amounts of other materials such as methane, carbon dioxide, nitrogen, and argon. The amount of these other materials depends on the composition of the hydrocarbons introduced to the reforming furnace and the configuration of the reforming furnace itself. The syngas can subsequently be converted into Fischer-Tropsch products, ammonia, and/or other useful products, as is known in the art.
Some hydrocarbon reforming furnaces include a radiant section in which a reformer tube is heated by radiant burners. Hydrocarbon can be fed to the reformer tube, which can be filled with catalyst. The reformer tube is heated by the radiant burners and an endothermic reaction can take place, in which at least a portion of the hydrocarbon stream is converted to carbon monoxide and hydrogen gas in the presence of steam. As the reaction is endothermic, the throughput rate can be limited by the heat transfer rate from the burners, through the reformer tube, to the hydrocarbon, among other limiting factors. To maximize radiant heat transfer, the burners are fired at high loads, resulting in high temperatures in the radiant section.
The bulk of the heat transfer to the reformer tube is radiant, generating a hot flue gas. The flue gas generated in the radiant section can be vented through an exhaust. To recover the heat from the flue gas, various convective heat transfer structures can be disposed in the exhaust. One such structure is known as a “pre-reformer,” which can use the recovered heat to at least partially reform the hydrocarbon prior to its entry into the reformer tube of the radiant section. Typically, the high temperature of the flue gas presents a challenge to recovering the flue gas heat in the pre-reformer as the structures can weaken and/or fail over time. What is needed, therefore, is an apparatus, method, and system for efficiently reforming hydrocarbon, while preserving a long useful life of the structure.